How does Batcache page caching work?

Page caching is one of the three levels of caching Pressable uses to ensure your site loads quickly and efficiently.

To achieve page caching, we use a drop-in plugin called Batcache, which is “symlinked” as advanced-cache.php in the wp-content folder on every Pressable site.

Batcache stores and serves rendered pages. In a nutshell, when your page receives two visits within a period of two minutes, a cached version of the page is stored on the second visit for five minutes. Future visitors will receive the cached version for five minutes, after which a fresh render of the site will be used.

To verify that your page is indeed being cached by Batcache, load the source code of your page. For example: view-source:https://kb.pressable.com/. You should see an HTML comment like this at the very bottom of the page:

Batcache will insert an HTML comment when it caches a page, as well as when it is serving a cached page.

Caching should work if your site is in Production Mode. However, there are cases where caching may not work. For example, if your site hasn’t been loaded twice in the last two minutes, there will not be a cached version of the page stored. Additionally, if pages on your site are loading cookies with the prefix wp or wordpress, Batcache exempts these pages from caching. It is also possible that your site is using custom caching rules that exempt certain pages from caching.